1. Field of the Invention
The present invention relates to a controller.
2. Description of the Related Art
When a storage device such as a Hard Disk Drive (HDD) used in a host device is replaced with a semiconductor storage device such as a flash memory, for example, the data stored in the HDD may be copied onto the flash memory. In the case where the HDD has a bad sector, the data that has been read from the sector address indicating the storage position of the bad sector is read as unrecoverable erroneous data (see, for example, JP-A 2005-293119 (KOKAI)). Accordingly, after the data has been copied onto the flash memory, when an access is to be made to the data storage location within the flash memory corresponding to the sector address of the bad sector, some measures need to be taken because the access is an access to the bad sector.
One method may be, for example, to register, into a table, a corresponding relationship between bad sectors and data storage locations within the flash memory so that, when an access is to be made to the flash memory, it is judged, for each access, whether the storage location to be accessed corresponds to a bad sector by referring to the table. An HDD has, however, a low possibility of having bad sectors. Accordingly, the possibility for the accessed storage location to correspond to a bad sector is also low. Considering these circumstances, it is inefficient to judge, for each access, whether the storage location corresponds to a bad sector by referring to the table. For this reason, there has been a demand for an improvement on the overall processing performance in semiconductor storage devices with regard to accesses made to special sectors such as bad sectors.